/*
 * Copyright (C) 2011 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.volley.toolbox;

import com.android.volley.Request;
import com.android.volley.Response;
import com.android.volley.VolleyError;

import java.util.concurrent.ExecutionException;
import java.util.concurrent.Future;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.TimeoutException;

/**
 * A Future that represents a Volley request.
 * Used by providing as your response and error listeners. For example:
 * <pre>
 * RequestFuture&lt;JSONObject&gt; future = RequestFuture.newFuture();
 * MyRequest request = new MyRequest(URL, future, future);
 * // If you want to be able to cancel the request:
 * future.setRequest(requestQueue.add(request));
 * // Otherwise:
 * requestQueue.add(request);
 * try {
 *   JSONObject response = future.get();
 *   // do something with response
 * } catch (InterruptedException e) {
 *   // handle the error
 * } catch (ExecutionException e) {
 *   // handle the error
 * }
 * </pre>
 * @param <T> The type of parsed response this future expects.
 */
public class RequestFuture< T > implements Future< T >, Response.Listener< T >, Response.ErrorListener
{
	private Request< ? > mRequest;
	private boolean mResultReceived = false;
	private T mResult;
	private VolleyError mException;
	
	public static < E > RequestFuture< E > newFuture()
	{
		return new RequestFuture< E >();
	}
	
	private RequestFuture()
	{
	}
	
	public void setRequest( Request< ? > request )
	{
		mRequest = request;
	}
	
	@Override
	public synchronized boolean cancel( boolean mayInterruptIfRunning )
	{
		if( mRequest == null )
		{
			return false;
		}
		
		if( !isDone() )
		{
			mRequest.cancel();
			return true;
		}
		else
		{
			return false;
		}
	}
	
	@Override
	public T get() throws InterruptedException, ExecutionException
	{
		try
		{
			return doGet( null );
		}
		catch( TimeoutException e )
		{
			throw new AssertionError( e );
		}
	}
	
	@Override
	public T get(
			long timeout,
			TimeUnit unit ) throws InterruptedException, ExecutionException, TimeoutException
	{
		return doGet( TimeUnit.MILLISECONDS.convert( timeout, unit ) );
	}
	
	private synchronized T doGet( Long timeoutMs ) throws InterruptedException, ExecutionException, TimeoutException
	{
		if( mException != null )
		{
			throw new ExecutionException( mException );
		}
		
		if( mResultReceived )
		{
			return mResult;
		}
		
		if( timeoutMs == null )
		{
			wait( 0 );
		}
		else if( timeoutMs > 0 )
		{
			wait( timeoutMs );
		}
		
		if( mException != null )
		{
			throw new ExecutionException( mException );
		}
		
		if( !mResultReceived )
		{
			throw new TimeoutException();
		}
		
		return mResult;
	}
	
	@Override
	public boolean isCancelled()
	{
		if( mRequest == null )
		{
			return false;
		}
		return mRequest.isCanceled();
	}
	
	@Override
	public synchronized boolean isDone()
	{
		return mResultReceived || mException != null || isCancelled();
	}
	
	@Override
	public synchronized void onResponse( T response )
	{
		mResultReceived = true;
		mResult = response;
		notifyAll();
	}
	
	@Override
	public synchronized void onErrorResponse( VolleyError error )
	{
		mException = error;
		notifyAll();
	}
}

